ergo
template_blas_nrm2.h
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1 /* Ergo, version 3.8, a program for linear scaling electronic structure
2  * calculations.
3  * Copyright (C) 2019 Elias Rudberg, Emanuel H. Rubensson, Pawel Salek,
4  * and Anastasia Kruchinina.
5  *
6  * This program is free software: you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License as published by
8  * the Free Software Foundation, either version 3 of the License, or
9  * (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14  * GNU General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program. If not, see <http://www.gnu.org/licenses/>.
18  *
19  * Primary academic reference:
20  * Ergo: An open-source program for linear-scaling electronic structure
21  * calculations,
22  * Elias Rudberg, Emanuel H. Rubensson, Pawel Salek, and Anastasia
23  * Kruchinina,
24  * SoftwareX 7, 107 (2018),
25  * <http://dx.doi.org/10.1016/j.softx.2018.03.005>
26  *
27  * For further information about Ergo, see <http://www.ergoscf.org>.
28  */
29 
30  /* This file belongs to the template_lapack part of the Ergo source
31  * code. The source files in the template_lapack directory are modified
32  * versions of files originally distributed as CLAPACK, see the
33  * Copyright/license notice in the file template_lapack/COPYING.
34  */
35 
36 
37 #ifndef TEMPLATE_BLAS_NRM2_HEADER
38 #define TEMPLATE_BLAS_NRM2_HEADER
39 
40 
41 template<class Treal>
42 Treal template_blas_nrm2(const integer *n, const Treal *x, const integer *incx)
43 {
44 /* The following loop is equivalent to this call to the LAPACK
45  auxiliary routine:
46  CALL DLASSQ( N, X, INCX, SCALE, SSQ ) */
47  /* System generated locals */
48  integer i__1, i__2;
49  Treal ret_val, d__1;
50  /* Local variables */
51  Treal norm, scale, absxi;
52  integer ix;
53  Treal ssq;
54 /* DNRM2 returns the euclidean norm of a vector via the function
55  name, so that
56  DNRM2 := sqrt( x'*x )
57  -- This version written on 25-October-1982.
58  Modified on 14-October-1993 to inline the call to DLASSQ.
59  Sven Hammarling, Nag Ltd.
60  Parameter adjustments */
61  --x;
62  /* Function Body */
63  if (*n < 1 || *incx < 1) {
64  norm = 0.;
65  } else if (*n == 1) {
66  norm = absMACRO(x[1]);
67  } else {
68  scale = 0.;
69  ssq = 1.;
70 
71 
72  i__1 = (*n - 1) * *incx + 1;
73  i__2 = *incx;
74  for (ix = 1; i__2 < 0 ? ix >= i__1 : ix <= i__1; ix += i__2) {
75  if (x[ix] != 0.) {
76  absxi = (d__1 = x[ix], absMACRO(d__1));
77  if (scale < absxi) {
78 /* Computing 2nd power */
79  d__1 = scale / absxi;
80  ssq = ssq * (d__1 * d__1) + 1.;
81  scale = absxi;
82  } else {
83 /* Computing 2nd power */
84  d__1 = absxi / scale;
85  ssq += d__1 * d__1;
86  }
87  }
88 /* L10: */
89  }
90  norm = scale * template_blas_sqrt(ssq);
91  }
92 
93  ret_val = norm;
94  return ret_val;
95 
96 /* End of DNRM2. */
97 
98 } /* dnrm2_ */
99 
100 #endif
template_blas_sqrt
Treal template_blas_sqrt(Treal x)
absMACRO
#define absMACRO(x)
Definition: template_blas_common.h:47
template_blas_nrm2
Treal template_blas_nrm2(const integer *n, const Treal *x, const integer *incx)
Definition: template_blas_nrm2.h:42
integer
int integer
Definition: template_blas_common.h:40